The present invention generally relates to rotary recording medium reproducing apparatuses having a rotary recording medium clamping device, and more particularly to a rotary recording medium reproducing apparatus having a device constructed to automatically and stably clamp a rotary recording medium placed onto a turntable at the center part of the rotary recording medium.
Conventionally, apparatuses for reproducing rotary recording mediums of a so-called electrostatic capacitance type have been reduced into practical use. In this reproducing apparatus, a reproducing stylus makes contact with and slides along a recorded track of the rotary recording medium (hereinafter simply referred to as a disc) in which an information signal such as a video signal is recorded as a variation in geometrical configuration, to reproduce the recorded signal as variations in electrostatic capacitance between the disc and an electrode of the reproducing stylus. In this type of a rotary recording medium reproducing apparatus, the disc must be clamped on the turntable so that the disc can rotate with a stable rotating surface upon reproduction, in order ro perform stable reproduction.
A device for clamping a disc on the turntable was previously proposed in a U.S. patent application Ser. No. 249,738 entitled "DISC-SHAPED RECORDING MEDIUM REPRODUCING APPARATUS" filed Mar. 31, 1981, in which the assignee is the same as that of the present application. This disc clamping device rotates unitarily with the turntable, however, moves up and down independently from the turntable. Clamping fingers made of a ferromagnetic material are provided on supporting members which support the part in the vicinity of the center hole of the disc when the disc clamping device is at a raised position. Further, permanent magnet pieces were provided at corresponding positions where the support members are lowered. The clamping claws are held at non-operational positions by springs, when the support members are at raised positions. On the other hand, the clamping fingers are attracted by the permanent magnet pieces and rotated, when the support members are lowered in a state where the disc is supported by these support members, to clamp the disc onto the turntable. Accordingly, special parts such as the springs and permanent magnet pieces were required, and the construction of the apparatus became complex. Moreover, there was a disadvantage in that the cost of the apparatus became high, due to the troublesome operations involved upon assembling of the apparatus.